Damage evolution in thermal barrier coating under thermal gradient mechanical fatigue loading

This research aims to clarify the driving forces behind interfacial damage in thermal barrier coatings associated with buckling-driven delamination. Using an artificial interfacial defect processed by laser shock, thermomechanical fatigue loadings are investigated both with or without a through-thickness temperature gradient. In situ infrared imaging enables the tracking of further debonding, allowing assessment of the influence of complex loading conditions on the interfacial damage rate. Based on these findings, a clear ranking of the influence of thermomechanical fatigue parameters is established, including temperature, temperature gradient, cooling rate, strain level, and stress relaxation during dwell time at maximum temperature. A sensitivity analysis was carried out using a finite element method, considering temperature gradients and the realistic geometry of the blister. Through-thickness gradients were shown to increase the maximum stress intensity factors at the interface, driving monotonic damage of the interface. The interface temperature and the local strain amplitude govern the stress intensity factor amplitude and subsequent interfacial toughness decrease, driving fatigue damage of the interface. • Thermal barrier coatings with processed blisters undergo thermomechanical gradient fatigue tests. • Interfacial damage rate is monitored in situ by infra red thermography. • Through thickness gradients is observed to yield local ratchetting. • Thermal gradients and mechanical loadings drive interfacial monotonic damage. • Fatigue damage induces decrease in interfacial toughness.